You buy them at the black market @ chao kindergarden.
You buy it. Go to the Chao kindergarten and on the left hand side their is a shop. The shops items switch from time to time but yellow is a quite common egg.
yes
Get a lot of emblems
Collect emblems
Get emblems
You need to have at least iver 25 emblems to get a green egg in sonic adventure 2 battle
gold egg
No
You have to buy it
Collect emblems
Collect a lot of emblems
You need a gameboy advance and a dual link
20